It has long been known that hydrophilic coatings with low friction (coefficient of friction of 0.3 or less) are useful for a variety of medical devices such as catheters, catheter introducers, guidewires and the like having an organic substrate or an inorganic substrate. When low friction surfaces are used, the devices, upon introduction into the body, slide easily within arteries, veins, cannula and other body orifices and passageways. There have been a wide variety of methods used to provide the surfaces desired. In some cases the material of the catheter or medical device is formed of a material having good anti-friction properties such as poly(tetrafluoroethylene) or other plastics which tend to avoid abrasion with the body. However, in many cases the selection of materials does not provide the anti-slip properties desired in conjunction with other desirable properties of the particular medical device. In other cases the desired adherence to a particular substrate is not achieved.
The art has recognized that polymer surfaces can be provided with hydrophilic coatings formed by the combinations of certain polymers, both non-cross linked and cross-linked with a hydrophilic polymer like polyvinylpyrrolidone (PVP) or poly(ethylene oxide) (PEO).
For example, U.S. Pat. Nos. 5,077,352, 5,160,790, 5,179,174 and 5,290,585 to ELTON each discloses a flexible, lubricous organic coating formed by applying a mixture of an isocyanate, a polyol, a hydrophilic polymer like poly (ethylene oxide) (PEO) or polyvinylpyrrolidone (PVP) and a carrier liquid to a surface to be coated. The carrier liquid is removed and the mixture reacted to form a lubricous, flexible homogenous coating of crosslinked polyurethane linkages complexed with PVP or PEO particularly suitable for use as a protective lubricous coating on medical devices introduced into the body. For convenience sake the aforementioned crosslinked coatings will be referred to herein as crosslinked polyurethane/PEO coatings (e.g. see U.S. Elton Pat. Nos. 5,077,352 and 5,179,174) and crosslinked polyurethane/PVP coatings (see U.S. Elton Pat. Nos. 5,160,790 and 5,290,585) and the disclosures of the aforementioned patents are incorporated herein by reference.
The use of a crosslinked polyurethane complexed with poly(ethylene oxide) (PEO) or polyvinylpyrrolidone (PVP) has proven to be an effective, lubricous and durable coating on numerous organic substrates. However, there are several organic substrates and numerous inorganic and organometallic substrates (glass, ceramic, metal, silicone, etc.) that first require surface treatment/modification to provide an effective lubricous, durable coating when aforementioned polyurethane complexed with PEO or PVP coatings are applied.
Examples of additional crosslinked polymers complexed with PEO or PVP which provide effective lubricious and durable coatings on various substrates, are those coating compositions disclosed in copending application Ser. No. 08/746,976 filed Nov. 18, 1996 relating to crosslinked polyurea polymers complexed with PEO or PVP coatings as well as coating compositions disclosed in copending application Ser. No. 08/751,405 filed Nov. 18, 1996 relating to crosslinked polyurethaneurea polymers complexed with PEO or PVP.
The disclosure of the aforementioned copending applications are incorporated herein by reference.
The above mentioned crosslinked polyurea/PEO or PVP coatings are formed from the curing of the product resulting from the reaction of an isocyanate and a compound having at least two active hydrogens per molecule selected from the group consisting of polyamines, polymercaptans, and polycarboxylates or compounds with NH, NH.sub.2, SH or COOH groups on same molecule, in the presence of the hydrophilic PEO or PVP polymer, with the total sum of the average isocyanate functionality plus the average active hydrogen functionality exceeding 4 and the molar ratio of total NCO groups to total active hydrogens being at least 0.8.
The earlier mentioned crosslinked polyurethaneurea/PEO or PVP coatings are formed from the curing of the product resulting from the reaction of an isocyanate and a polyol in the presence of the PEO or PVP polymer, the stoichiometric ratio of the total NCO groups in the isocyanate to total OH groups in the polyol is such that the resulting polymer formed is a crosslinked polyurethaneurea polymer.
For convenience sake the earlier mentioned crosslinked polyurethane, polyurea or polyurethaneurea polymers complexed with PEO or PVP will be referred to hereinafter as polyurethane, polyurea or polyurethaneurea/PEO or PVP coatings.
An object of this invention is to provide a two step method or process for applying a coating of crosslinked polyurethane, polyurea or polyurethaneurea/PEO or PVP wherein the first step involves providing a substrate with a functional tie layer in such a manner that the treated tie layer surface is rendered more receptive to adhering or bonding with the crosslinked polyurethane, polyurea or polyurethaneurea/PEO or PVP coating resulting from the second step of the two step method of this invention.
Accordingly, an object of this invention is to provide a two step method for improving the adherence or bonding of a crosslinked polyurethane, polyurea or polyurethaneurea/PEO or PVP to a substrate of a medical device that otherwise would render said coatings not fully suitable as an effective, lubricous, durable coating for said substrate.
A further object of this invention is to provide medical devices whose outer surface is provided with an effective, lubricous and durable coating which resists wear when the coated surface is moved with respect to an adjacent surface. A still further object of this invention is to provide a medical device where inner and/or outer surface exhibits improved lubricity when hydrated with water and/or other aqueous solutions such as blood, urine or other body fluids.